Interferometric modulation of radiation

ABSTRACT

An Interferometric Modulator (IMod) is a microelectromechanical device for modulating light using interference. The colors of these devices may be determined in a spatial fashion, and their inherent color shift may be compensated for using several optical compensation mechanisms. Brightness, addressing, and driving of IMods may be accomplished in a variety of ways with appropriate packaging, and peripheral electronics which can be attached and/or fabricated using one of many techniques . The devices may be used in both embedded and directly perceived applications, the latter providing multiple viewing modes as well as a multitude of product concepts ranging in size from microscopic to architectural in scope.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This is a continuation in part of U.S. patent applications Ser.Nos. 08/238,750, and 08/554,630, filed May 5, 1995, and Nov. 5, 1995,respectively, and incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] This invention relates to visible spectrum (which we define toinclude portions of the ultra-violet and infrared spectra) modulatorarrays and interferometric modulation.

[0003] The first patent application cited above describes two kinds ofstructures whose impedance, the reciprocal of admittance, can beactively modified so that they can modulate light. One scheme is adeformable cavity whose optical properties can be altered bydeformation, electrostatically or otherwise, of one or both of thecavity walls. The composition and thickness of these walls, whichcomprise layers of dielectric, semiconductor, or metallic films, allowsfor a variety of modulator designs exhibiting different opticalresponses to applied voltages.

[0004] The second patent application cited above describes designs whichrely on an induced absorber. These designs operate in reflective modeand can be fabricated simply and on a variety of substrates.

[0005] The devices disclosed in both of these patent applications arepart of a broad class of devices which we will refer to as IMods (shortfor “interferometric modulators”). An IMod is a microfabricated devicethat modulates incident light by the manipulation of admittance via themodification of its interferometric characteristics.

[0006] Any object or image supporter which uses modulated light toconvey information through vision is a form of visual media. Theinformation being conveyed lies on a continuum. At one end of thecontinuum, the information is codified as in text or drawings, and atthe other end of the continuum, it is abstract and in the form ofsymbolic patterns as in art or representations of reality (a picture).

[0007] Information conveyed by visual media may encompass knowledge,stimulate thought, or inspire feelings. But regardless of its function,it has historically been portrayed in a static form. That is, theinformation content represented is unchanging over time. Statictechniques encompass an extremely wide range, but in general includesome kind of mechanism for producing variations in color and/orbrightness comprising the image, and a way to physically support themechanism. Examples of the former include dyes, inks, paints, pigments,chalk, and photographic emulsion, while examples of the latter includepaper, canvas, plastic, wood, and metal.

[0008] In recent history, static display techniques are being displacedby active schemes. A prime example is the cathode ray tube (CRT), butflat panel displays (FPD) offer promise of becoming dominant because ofthe need to display information in ever smaller and more portableformats.

[0009] An advanced form of the FPD is the active matrix liquid crystaldisplay (AMLCD). AMLCDs tend to be expensive and large, and are heavyusers of power. They also have a limited ability to convey visualinformation with the range of color, brightness, and contrast that thehuman eye is capable of perceiving, using reflected light, which is howreal objects usually present themselves to a viewer. (Few naturallyoccurring things emit their own light.)

[0010] Butterflies, on the other hand, achieve a broad range of color,brightness, and contrast, using incident light, processedinterferometrically, before delivery to the viewer.

SUMMARY

[0011] In general, in one aspect, the invention features a modulator oflight having an interference cavity for causing interference modulationof the light, the cavity having a mirror, the mirror having a corrugatedsurface.

[0012] In general, in another aspect of the invention, the interferencemodulation of the light produces a quiescent color visible to anobserver, the quiescent color being determined by the spatialconfiguration of the modulator.

[0013] In implementations of the invention, the interference cavity mayinclude a mirror and a supporting structure holding the mirror, and thespatial configuration may include a configuration of the supportingstructure, or patterning of the mirror. The supporting structure may becoupled to a rear surface of the mirror. The invention eliminates theneed for separately defined spacers and improves the fill-factor.

[0014] In general, in another aspect of the invention, the structure formodulating light includes modulators of light each including aninterference cavity for causing interference modulation of the light,each of the modulators having a viewing cone. The viewing cones of themodulators are aligned in different directions.

[0015] In implementations of the invention, the viewing cones of thedifferent modulators may be aligned in random directions and may benarrower than the viewing cone of the overall structure. Viewing arandomly oriented array of interference modulators effectively reducesthe color shift.

[0016] In general, in another aspect of the invention, the modulatorsmay be suspended in a solid or liquid medium.

[0017] In general, in another aspect of the invention, an opticalcompensation mechanism is coupled to the modulators to enhance theoptical performance of the structure. In implementations of theinvention, the mechanism may be a combination of one or more of aholographically patterned material, a photonic crystal array, amultilayer array of dielectric mirrors, or an array of microlenses. Thebrightness and/or color may be controlled by error diffusion. An arrayof modulators may be viewed through a film of material which, because ofits tailored optical properties, enhances the view from a limited rangeof angles, or takes incident light of random orientation and orders it.The film may also enhance the fill factor of the pixel. The film mayalso comprise a patterned light emitting material to providesupplemental lighting.

[0018] In general, in another aspect of the invention, an optical fiberis coupled to the interference cavity. The invention may be used in theanalysis of chemical, organic, or biological components.

[0019] In general, in another aspect of the invention, there is an arrayof interference modulators of light, a lens system, a media transportmechanism and control electronics.

[0020] In general, in another aspect, the invention features aninformation projection system having an array of interference modulatorsof light, a lens system, mechanical scanners, and control electronics.In implementations of the invention, the control electronics may beconfigured to generate projected images for virtual environments; andthe array may include liquid crystals or micromechanical modulators.

[0021] In general, in another aspect, the invention features anelectronics product having an operational element, a housing enclosingthe operational element and including a display having a surface viewedby a user, and an array of interference modulators of light on thesurface.

[0022] Implementations of the invention may include one or more of thefollowing features. The operational element may include a personalcommunications device, or a personal information tool, or a vehicularcontrol panel, or an instrument control panel, or a time keeping device.The array may substantially alter the aesthetic or decorative featuresof the surface. The aesthetic component may respond to a state of use ofthe consumer product. The array may also provide information. Themodulation array of the housing may comprise liquid crystals, fieldemission, plasma, or organic emitter based technologies and associatedelectronics.

[0023] In general, in another aspect, the invention features devices inwhich aggregate arrays of interference modulators are assembled as adisplay, e.g., as a sign or a billboard.

[0024] In general, in another aspect, the invention features a vehiclehaving a body panel, an array of interference modulators of light on asurface of the body panel, and electronic circuitry for determining theaesthetic appearance of the body panel by controlling the array ofinterference modulators.

[0025] In general, in another aspect, the invention features a buildingcomprising external surface elements, an array of interferencemodulators of light on a surface of the body panel, and electroniccircuitry for determining the aesthetic appearance of the surfaceelements by controlling the array of interference modulators.

[0026] In general, in another aspect, the invention features a fullcolor active display comprising a liquid crystal medium, andinterferometric elements embedded in the medium.

[0027] In general, in another aspect, the invention features a structureincluding a substrate, micromechanical elements formed on the substrate,and electronics connected to control the elements, the electronics beingformed also on the substrate.

[0028] Individual pixels of the array may consist of arrays ofsubpixels, allowing brightness and color control via the activation ofsome fraction of these subpixels in a process known as spatialdithering. Individual pixels or subpixel arrays may be turned on for afraction of an arbitrary time interval to control brightness in aprocess known as pulse width modulation (PWM). Individual pixels orsubpixel arrays may be turned on for a fraction of the time required toscan the entire array to control brightness in a process known as framewidth modulation (FWM). These two schemes are facilitated by theinherent hysteresis of the IMod which allows for the use of digitaldriver circuits. Neighboring pixels yield a brightness value which isthe average of the desired value when error diffusion is used.Brightness control may be achieved via a combination of spatialdithering, PWM/FWM, or error diffusion. Color control may be achieved bytuning individual colors to a particular color, or by combining pixelsof different colors and different brightness. The terms pixels and IModsare interchangeable, but in general, pixel refers to a controllableelement which may consist of one or more IMods or subpixels, and whichis “seen” directly or indirectly by an individual.

[0029] The arrays may fabricated on a solid substrate of some kind whichmay be of any material as long as it provides a surface, portions ofwhich are optically smooth. The material may be transparent or opaque.The material may be flat or have a contoured surface, or be the surfaceof a three dimensional object. The arrays may be fabricated on thesurface, or on the opposite or both sides if the substrate istransparent. In a further aspect the invention can be viewed in avariety of ways.

[0030] Implementations of the invention may include one or more of thefollowing features. The array may be directly viewed in that anindividual can look at the array and see the represented informationfrom any angle. The array may be directly viewed from a fixed angle. Thearray may be indirectly viewed in that the information is projected onto a secondary surface, or projected through an optical system, or both.

[0031] In yet another aspect the invention can be electricallycontrolled and driven in several ways.

[0032] Implementations of the invention may include one or more of thefollowing features. The array may be fabricated on a substrate and thedriver and controller electronics are fabricated on a separatesubstrate. The two substrates may be connected electrically or opticallyvia cables, or optically, magnetically, or via radio frequencies via afree space connection. The array may be fabricated with driver,controller, or memory electronics, or some combination thereof, mountedon the same substrate and connected via conducting lines. The array maybe fabricated on a substrate along with the driver, controller or memoryelectronics, or some combination thereof. The substrate may includeactive electronics which constitute driver, controller, or memoryelectronics, or some combination thereof, and the array may befabricated on the substrate. The electronics may be implemented usingmicroelectromechanical (MEM) devices.

[0033] In an additional aspect the invention modulates light actively,using an array of modulators or sections of arrays which are addressedin several ways.

[0034] Implementations of the invention may include one or more of thefollowing features. Individual pixels or arrays of pixels may beconnected to a single driver and may be activated independently of anyother pixel or pixel array in a technique known as direct addressing.Individual pixels or arrays of pixels may be addressed using atwo-dimensional matrix of conductors and addressed in a sequentialfashion in a technique known as matrix addressing. Some combination ofmatrix or direct addressing may be used.

[0035] Among the advantages of the invention are one or more of thefollowing.

[0036] Because interference modulators are fabricated on a singlesubstrate, instead of a sandwich as in LCDs, many more possible rolesare made available. The materials used in their construction areinsensitive to degradation by UV exposure, and can withstand muchgreater variations in temperature. Extremely saturated colors may beproduced. Extremely high resolutions make possible detail imperceptibleto the human eye. Either transmitted or reflected light may be used asan illumination source, the latter more accurately representing howobjects and images are perceived. The ability to fabricate these deviceson virtually any substrate makes possible the surface modulation ofessentially any man-made or naturally occurring object. It is possibleto realize images which are much closer to what exists in nature andmore realistic than what is possible using current printing methods.

[0037] Interferometric modulation uses incident light to give excellentperformance in terms of color saturation, dynamic range (brightness),contrast, and efficient use of incident light, performance which mayapproach the perceptual range of the human visual system. Thefabrication technology allows interference modulators to be manufacturedin a great variety of forms. This variety will enable active visualmedia (and superior static visual media) to become as ubiquitous as thetraditional static media which surround us.

[0038] In general, the invention provides the tools for creating anarray of products and environments which are as visually rich andstimulating as anything found in nature.

[0039] Other advantages and features will become apparent from thefollowing description and from the claims.

DESCRIPTION

[0040]FIGS. 1A and 1B are top and perspective views of an IMod withspatially defined color.

[0041]FIG. 2 is a side view of an IMod with spatially defined color.

[0042]FIGS. 3A and 3B are top and side views of a spatially definedmirror. FIG. 3A shows a mirror with a 50% etch while FIG. 3B shows amirror with a 75% etch.

[0043]FIG. 4 is a perspective view of a back-supported IMod with a goodfill factor.

[0044]FIGS. 5A, 5B, and 5C are schematic views of an IMod and IMod arraywith a limited viewing cone. FIG. 5A shows the behavior of light withinthe viewing cone while FIG. 5B shows the behavior of light outside thecone. FIG. 5C shows the performance of an overall array.

[0045]FIGS. 6A, 6B, 6C, 6D, and 6E, 6F are side views of opticalcompensation mechanisms used for minimizing color shift and enhancingfill factor. FIG. 6A shows a holographically patterned material, FIG. 6Bshows a photonic crystal array, FIG. 6C shows a multilayer dielectricarray, FIG. 6D shows an array of microlenses, while FIGS. 6E and 6F showside and top views of a supplemental lighting film.

[0046]FIGS. 7A and 7B are schematic views of an array which is addressedusing spatial dithering. FIG. 7A shows a full-color pixel while FIG. 7Bshows detail of a sub-pixel.

[0047]FIG. 8 is a timing diagram for driving a binary IMod.

[0048]FIG. 9 is a diagram of the hysteresis curve for an IMod device.

[0049]FIGS. 10A and 10B are a top view of an IMod array which isconnected for matrix addressing and a digital driver. FIG. 10A shows thematrix array while FIG. 10B shows a digital driving circuit.

[0050]FIG. 11 is a side view of an IMod array configured for directviewing.

[0051]FIG. 12 is a side view of an IMod array configured for directviewing through an optical system.

[0052]FIG. 13 is a diagram of an IMod array configured for indirectviewing.

[0053]FIG. 14 is a perspective view of an IMod array and a separatedriver/controller.

[0054]FIGS. 15 and 16 are perspective views of IMod arrays anddriver/controllers on the same substrates.

[0055]FIGS. 17A and 17B are front views of a direct driven IMod subarraydisplay. FIG. 17A shows a seven segment display while FIG. 17B showsdetail of one of the segments.

[0056]FIGS. 18A and 18B are top views of a matrix driven subarraydisplay. FIG. 18A shows a matrix display while FIG. 18B shows detail ofone of the elements.

[0057]FIG. 19 is a side view of an IMod based fiber optic endcapmodulator.

[0058]FIG. 20 is a perspective view of a linear tunable IMod array.

[0059]FIGS. 21A and 21B are a representational side view of a linearIMod array used in an imaging application and a components diagram. FIG.21A shows the view while FIG. 21B shows the components diagram.

[0060]FIG. 22 is a perspective view of a two-dimensional tunable IModarray.

[0061]FIG. 23 is a perspective view of a two-dimensional IMod array usedin an imaging application.

[0062]FIGS. 24A, 24B, 24C, 24D, and 24E are views of an IMod displayused in a watch application. FIG. 24A shows a perspective view of awatch display, FIGS. 24B, 24C, 24D, and 24E show examples of watchfaces.

[0063]FIGS. 25A and 25B are views of an IMod display used in a headmounted display application. FIG. 25A shows a head mounted display whileFIG. 25B shows detail of the image projector.

[0064]FIGS. 26A, 26B, 26C, and 26D are perspective views of an IModdisplay used in several portable information interface applications anda components diagram. FIG. 26A shows a portable information tool, FIG.26B shows the components diagram, FIG. 26C shows a cellular phone, whileFIG. 26D shows a pager.

[0065]FIGS. 27A, 27B, 27C, 27D, 27E, 27F and 27G are views of an IModdisplay used in applications for information and decorative display, aremote control, and components diagrams. FIGS. 27A, 27B, and 27D showseveral examples, FIG. 27C shows a components diagram, FIG. 27E shows aremote control, and FIG. 27F shows another components diagram.

[0066]FIGS. 28A and 28B are side views of an IMod display used in anapplication for automotive decoration and a components diagram. FIG. 28Ashows a decorated automobile while FIG. 28B shows the componentsdiagram.

[0067]FIGS. 29A, 29B, and 29C are views of an IMod array used as abillboard display and a components diagram. FIG. 29A shows a fullbillboard, FIG. 29B shows a display segment, FIG. 29C shows a segmentpixel, and FIG. 29D shows the components diagram.

[0068]FIGS. 30A and 30B are views of an IMod array used as anarchitectural exterior and a components diagram. FIG. 30A shows theskyscaper, while FIG. 30B shows the components diagram.

[0069]FIGS. 31A and 31B are drawings of a liquid crystal impregnatedwith an interferometric pigment. FIG. 31A shows the liquid crystal cellin the undriven state while FIG. 31B shows it in the driven state.

[0070]FIGS. 32A and 32B are drawings of an IMod array used in aprojection display and a components diagram. FIG. 32A shows theprojection system while FIG. 32B shows the components diagram.

[0071]FIGS. 33A and 33B are drawings of an IMod array used in anchemical detection device and a components diagram. FIG. 33A shows thedetection device while FIG. 33B shows the components diagram.

[0072]FIGS. 34A, 34B, and 34C are front and side views of an IMod basedautomotive heads up display and a components diagram. FIG. 34A shows thefront view, FIG. 34B shows the side view, and FIG. 34C shows thecomponents diagram.

[0073]FIGS. 35A and 35B are drawings of an IMod display used in aninstrument panel and a components diagram. FIG. 35A shows the panelwhile FIG. 35B shows the components diagram.

IMod Structures

[0074] Referring to FIGS. 1A and 1B, two IMod structures 114 and 116each include a secondary mirror 102 with a corrugated pattern 104 etchedinto its upper (outer) surface 103, using any of a variety of knowntechniques. The corrugation does not extend through the membrane 106 onwhich the mirror is formed so that the inner surface 108 of the mirrorremains smooth. FIG. 1B reveals the pattern of etched corrugation 104 onthe secondary mirror and the smooth inner surface 112 which remainsafter etch. The corrugated pattern, which can be formed in a variety ofgeometries (e.g., rectangular, pyramidal, conical), provides structuralstiffening of the mirror, making it more immune to variations inmaterial stresses, reducing total mass, and preventing deformation whenthe mirror is actuated.

[0075] In general, an IMod which has either no voltage applied or somerelatively steady state voltage, or bias voltage, applied is consideredto be in a quiescent state and will reflect a particular color, aquiescent color. In the previously referenced patent applications, thequiescent color is determined by the thickness of the sacrificial spacerupon which the secondary mirror is fabricated.

[0076] Each IMod 114, 116 is rectangular and connected at its fourcorners to four posts 118 via support arms such as 120 and 122. In somecases (see discussion below), the IMod array will be operated at astated constant bias voltage. In those cases, the secondary mirror 102will always maintain a quiescent position which is closer tocorresponding primary mirror 128 than without any bias voltage applied.The fabrication of IMods with differently sized support arms allows forthe mechanical restoration force of each IMod to be determined by itsgeometry. Thus, with the same bias voltage applied to multiple IMods,each IMod may maintain a different biased position (distance from theprimary mirror) via control of the dimensions of the support arm and itsresulting spring constant. The thicker the support arm is, the greaterits spring constant. Thus different colors (e.g., red, green, and blue)can be displayed by different IMods without requiring deposition ofdifferent thickness spacers. Instead, a single spacer, deposited andsubsequently removed during fabrication, may be used while color isdetermined by modifying the support arm dimensions during the singlephotolithographic step used to define the arms. For example, in FIG. 2,IMods 114, 116 are both shown in quiescent states with the same biasvoltage applied. However, the gap spacing 126 for IMod 114 is largerthan gap spacing 128 for IMod 116 by virtue of the larger dimensions ofits respective support arms.

[0077] As shown in FIGS. 3A and 3B, in another technique for achievingspatially defined color, instead of affecting the quiescent position ofthe movable membrane, one or both of the mirrors (walls) comprising theIMod is patterned to determine its qualities spatially instead of bymaterial thickness.

[0078] Thus, in FIG. 3A, mirror 300 has two layers 302 and 304. Byetching layer 302 the effective index of refraction of layer 302, andthus the performance of mirror 300, may be altered by controlling thepercentage of the layer which remains after the etch. For example, amaterial with index of 2 maintains that value if there is no etch atall. However if 75% of the material is etched away, the average indexfalls to 1.75. Etching enough of the material results in an index whichis essentially that of air, or of the material which may fill in theetched area.

[0079] The mirror layer 308 in FIG. 3B, by contrast has an effectiverefractive index which is less than that of mirror layer 302. Becausethe overall behavior of both mirrors is determined by their materialsproperties, and the behavior of the IMod by the mirror properties, thenthe color of an IMod incorporating mirror 300 is different from an IModcomprising mirror 306 by virtue of spatially varying, e.g., etching orpatterning, one or more of the layers comprising the mirrors. This,again, can be done in a single photolithographic step.

[0080] Referring to FIG. 4, in another type of IMod a back supportingmechanism is used instead of an array of posts and support arms (whichconsume useful surface area on the display). Here, the secondary mirror402 is mechanically held by support arm 400 at location 406. Arm 400contacts the substrate 403 at locations 408 where it occupies a minimalfootprint, thereby maximizing the amount of area devoted to the mirrors402, 404. This effect is enhanced by notches 408, 410 which allowmirrors 402 and 404 to conform to the support. Rear support could alsobe achieved in other ways, perhaps using multiple arms to maintainparallelism. The rear supports can also provide a basis for multilevelconductor lines. For example, an elevated conductor line 412 may be tiedto support arm 400. This configuration minimizes the area on thesubstrate required for such purposes.

Reducing Color Shift and Supplying Supplemental Illumination

[0081] As shown in FIGS. 5A through 5C, to minimize color shift as theangle of incidence changes (a characteristic of interferometricstructures) IMod structures 502, 506 are fabricated to have a very highaspect ratio, i.e., they are much taller than they are wide.Consequently, they only exhibit interferometric behavior within a narrowcone 501 of incidence angles. Incident light 500 which is within cone501, as in FIG. 5A, interacts with the multiple layers (shown by stripedsections in the figure) the composition and configuration of which aredictated by the the design of the IMod. In general, as indicated in theprevious patent applications, these can consist of combinations of thinfilms of metals, metallic oxides, or other compounds. The important factbeing that the geometry of the stack dictates that interference occursonly within a narrow cone of incidence angles. On the other hand, asseen in FIG. 5B, incident light 504 (outside of the cone) is relativelyunaffected by the IMod because it interacts with only a very few layers.Such an IMod would appear, say blue, to a viewer who looks at it from anarrow range of angles.

[0082] As seen in FIG. 5C, if an array 507 of these structures 508 isfabricated such that they are oriented to cover many different viewingangles then the entire array can appear blue from a much larger range ofangles. This random orientation may be achieved, for example, byfabrication on a randomly oriented surface or by random suspension in aliquid medium.

[0083] As seen in FIGS. 6A-6F, other techniques for minimizing colorshift and for supplying supplemental illumination are possible. In theseexamples, a specially designed optical film is fabricated on theopposite surface of the substrate from the surface on which the IModarray resides. Such films can be designed and fabricated in a number ofways, and may be used in conjunction with each other.

[0084] In FIG. 6A, film 600 is a volume or surface relief holographicfilm. A volume holographic film may be produced by exposing aphotosensitive polymer to the interference pattern produced by theintersection of two or more coherent light sources (i.e. lasers). Usingthe appropriate frequencies and beam orientations arbitrary periodicpatterns of refractive indices witin the film may be produced. A surfacerelief holographic film may be produced by creating a metal master usingany number of microfabrication techniques known by those skilled in theart. The master is subsequently used to the pattern into the film. Suchfilms can be used to enhance the transmission and reflection of lightwithin a definable cone of angles, thus minimizing off-axis light. Thecolors and brightness of a display viewed with on axis light areenhanced and color shift is diminished because brightness goes downsignificantly outside of the cone.

[0085] In FIG. 6B, another approach is shown as device 604 in which anarray of structures 606 is fabricated on the substrate. Thesestructures, which can be fabricated using the techniques described inthe previously referenced patent applications, can be consideredphotonic crystals, as described in the book “Photonic Crystals”, by JohnD. Joannopoulos, et al., and incorporated by reference. They areessentially three-dimensional interferometric arrays which demonstrateinterference from all angles. This provides the ability to designwaveguides which can perform a number of functions including channelingincident light of certain frequencies to the appropriately coloredpixels, or by changing light of a certain incidence angle to a newincidence angle, or some combination of both.

[0086] In another example, seen in FIG. 6C, a three-layer polymeric film610 contains suspended particles 611. The particles are actually singleor multi-layer dielectric mirrors which have been fabricated in the formof microscopic plates. These plates, for example, may be fabricated bydeposition of multilayer dielectric films onto a polymer sheet which,when dissolved, leaves a film which can “ground up” in a way whichproduces the plates. The plates are subsequently mixed into a liquidplastic precursor. By the application of electric fields during thecuring process, the orientation of these plates may be fixed duringmanufacture. The mirrors can be designed so that they only reflect at arange of grazing angles. Consequently, light is either reflected ortransmitted depending on the incidence angle with respect to the mirror.In this case, layer 612 is oriented to reflect light 609 of highincidence that enters the film 610 closer to the perpendicular. Layer614 reflects light 613 of lower incidence into a more perpendicularpath. Layer 616 modifies the even lower angle incident light 615.Because the layers minimally affect light which approachesperpendicularly, they each act as a separate “angle selective incidencefilter” with the result that randomly oriented incident light couplesinto the substrate with a higher degree of perpendicularly; Thisminimizes the color shift of a display viewed through this film.

[0087] In another example, FIG. 6D, micro lenses 622 are used in anarray in device 620. Each lens 622 may be used to enhance the fillfactor of the display by effectively magnifying the active area of eachpixel. This approach could be used by itself or in conjunction with theprevious color shift compensation films.

[0088] In another example, FIG. 6E, device 624 uses supplementallighting in the form of a frontlighting array. In this case an organiclight emitting material 626, for example, Alq/diamine structures andpoly(phenylene vinylene), can be deposited and patterned on thesubstrate. The top view, FIG. 6F, reveals a pattern 627 whichcorresponds with the IMod array underneath. That is, the light emittingareas 626 are designed to obscure the inactive areas between the IMods,and allow a clear aperture in the remaining regions. Light is emittedinto the substrate onto the IMod and is subsequently reflected back tothe viewer. Conversely, a patterned emitting film may be applied to thebackplate of the display and light transmitted forward through the gapsbetween the sub-pixels. By patterning a mirror on the front of thedisplay, this light can be reflected back upon the IMod array.Peripherally mounted light sources in conjunction with films relying ontotal internal reflection are yet another approach.

Brightness Control

[0089] Referring to FIG. 7A, a full color spatially dithered pixel 701includes side-by-side sub-pixels 700, 702, and 704. Sub-pixel 700, forexample, includes sub-arrays of IMods whose numbers differ in a binaryfashion. For example, sub-array 706 is one IMod, sub-array 708 is 2IMods, sub-array 710 is 4 IMods, while sub-array 718 is 128 IMods.Sub-array 712 is shown in greater detail in FIG. 7B. In the arrays, eachIMod is the same size so that the amount of area covered by eachsub-array is proportional to the total number of IMods in the array. Rowelectrodes 724 and column electrodes 722 are patterned to allow for theselective and independent actuation of individual sub-arrays.Consequently, the overall brightness of the pixel may be controlled byactuating combinations of the sub-arrays using a binary weightingscheme. With a total of 8 sub-arrays, each sub-pixel is capable of 256brightness levels. A brightness value of 136 may be achieved, forexample, by the actuation of sub-arrays 718 and 712. Color is obtainedby combining different values of brightness of the three sub-pixels.

[0090] The apparent dynamic range of the display may also be enhancedusing a process known as error diffusion. In some applications, thenumber of bits available for representing the full range of brightnessvalues (dynamic range) may be limited by the capabilities of thedrivers, for example. In such a situation, the dynamic range may beenhanced by causing neighboring pixels to have a brightness value, theaverage of which is closer to an absolute value that cannot be obtainedgiven the set number of bits. This process is accomplishedelectronically within the controller logic, and can be accomplishedwithout significantly affecting the display resolution.

Digital Driving

[0091] In a digital driving scheme, as shown in FIGS. 8, 9, and 10, FIG.8 is a timing diagram showing one set of voltages required to actuate amatrix addressed array of IMods. Column select pulses 800 and 802 arerepresentative of what would be applied to a particular column. Furtherdetail is revealed in pulse 800 which is shown to switch from voltagelevel Cbias to voltage Cselect. Row select pulses 804 and 806 are alsoshown, with 804 revealing that the required voltage levels are Rselect,Rbias, and Roff (0 volts). When a column select pulse is present, and arow select pulse is applied, the pixel which resides at the intersectionof the two is actuated as shown in the case of pixel 808 which resideson the row driven by select pulse 804, and subsequently in pixel 810,which resides on the row driven by pulse 806. When select pulse 804 isdriven to the Roff level, pixel 808 is turned off. Pixel 812 illustratesthe behavior of a pixel in an arbitrary state when a Roff value isplaced on the row line, i.e., if it is on it turns off, or if it is offit remains off.

[0092] In FIG. 9, the voltages are shown in the context of a hysteresiscurve which is typical of an IMod. As the applied voltage is increased,the membrane does not move significantly until the value rises beyond acertain point, which is known as the collapse threshold. After thispoint, the membrane undergoes full displacement. This state ismaintained until the voltage is dropped below a point where actuationbegan. Several conditions must be met in order for this scheme to besuccessful. The combination of Csel and Rsel must be higher than thecollapse threshold voltage, the combination of Cbias and Rsel must notfully actuate the membrane, the combination of Cbias and Rbias mustmaintain a displaced state, and the combination of Roff and Cbias mustfree the membrane.

[0093]FIG. 10A is representative of a typical matrix addressed arrayillustrating column lines 1000 and row lines 1002. FIG. 10B illustratesa typical shift register based driver circuit. The size of the displayarray and the number of bits in the register would determine how many ofthese components would be required for both rows and columns. Bitscorresponding to the appropriate row and column values are shifted intothe register and loaded on the outputs when they are required during thecourse of the scanning the display.

Viewing Modes

[0094] Referring to FIGS. 11, among the different generic ways to viewan IMod display 1104 (the best one being selected based on theparticular product application) are a direct viewing mode with theviewer 1100 perceiving the display without the aid of an image formingoptical system. Direct viewing can occur in reflection mode, usingreflected light 1102, or transmitted mode, using transmitted light 1106,or some combination of the two.

[0095] In another example, FIG. 12, direct viewing configurations mayrely on intervening optics to form an image from an image sourcegenerated by IMod display 1204. Reflected light 1202 or transmittedlight 1212, or a combination of the two, may be manipulated by macrolens system 1206. A more complicated or space critical application mightrequire more elaborate optics. In such a case, a lens system might beimplemented using a micro-lens array 1208 with or without the aid ofredirection mirrors 1214.

[0096] In FIG. 13, indirect viewing may be achieved with respect to animage generated by display 1304 using either transmitted light 1310 orreflected light 1301 from light source 1300. Lens system 1302 is thenused to form an image on viewing surface, 1306, which is where theviewer perceives the image.

Packaging and Driving Electronics

[0097] Referring to FIGS. 14 through 16, different techniques forpackaging and providing driver electronics are illustrated in order ofdegree of integration. FIG. 14 shows a configuration requiring twoseparate substrates. The IMod display array resides on substrate 1400which could be any one of a variety of materials described in thereferenced patent applications. The IMod array is not shown because itis obscured by backplate 1404, which is bonded to substrate 1400 viaseal 1402. Backplate 1404 can also be of a number of different materialswith the primary requirement being that it be impermeable to water, andthat its thermal coefficient of expansion be close to that of thesubstrate. Seal 1402 can be achieved in a number of ways. One approachinvolves the application of an epoxy but this results in the generationof gases during the curing process which may interfere with theoperation of the devices. Another approach involves fusion or eutecticbonding which utilizes heat to create a chemical or diffusion bondbetween two materials, in this case the substrate and the backplate.This process may be enhanced by forming a bead, in the form of seal1402, of additional materials such as silicon, aluminum, or other alloyswhich tend to bond well. This process may be further enhanced using atechnique known as anodic bonding. This is similar to fusion bondingexcept that a voltage potential is applied across the backplate andsubstrate. This allows the bond to occur at a lower temperature. Othertechniques are also possible.

[0098] The electronics 1410 comprise all of the row and column drivers,memory, and controller logic required to actuate the IMods in acontrolled fashion. Exactly where each of these functions reside woulddepend on the application and degree of integration required for anapplication. Specific examples will be discussed in subsequent portionsof this patent application. In FIG. 14, the drive electronics 1410 areshown mounted on substrate 1412. A connection is made between thissubstrate 1412 and the display substrate 1400, by ribbon cable 1408 andsubsequently to the display array via conductors 1406. Many techniquesexist for patterning the fine array of conductors for ribbon cable, aswell as for connecting them to disparate substrates.

[0099]FIG. 15 shows a display where the electronics have been mounted onthe display substrate. Display substrate 1500 serves as a support notonly for the IMod array but also for the integrated circuits 1508.Conductors 1506 are patterned to create appropriate paths between theICs and the array. ICs 1508 may be mounted on the substrate using anumber of techniques including TAB mounting and chip-on-glass techniqueswhich rely on anisotropically conducting films.

[0100]FIG. 16 shows a display which includes fully integratedelectronics and can be achieved in two fundamental ways.

[0101] In one case, substrate 1600 is an electronically inactive mediumupon which the IMod array and electronics 1608 are fabricated separatelyor in a fabrication process with some overlap. Electronics may befabricated using a number of techniques for building thin filmtransistors using materials such as amorphous silicon, polysilicon, orcadmium selenide. Electronics may also be fabricated usingmicroelectromechanical (MEM) switches instead of, or in conjunction withthin film transistors. All of these materials are deposited on thesurface of the substrate, and provide the electronically orelectromechanically active medium for circuits. This implementationdemonstrates a powerful approach to surface micromachining, which couldbe described as epi-fab. Essentially, in epi-fab all components of anymicroelectromechanical structure, both the mechanical and theelectronic, are fabricated entirely on the surface of an inertsubstrate.

[0102] In the second case, the substrate is active silicon or galliumarsenide and the electronics are fabricated as a part of it. The IModarray is then fabricated on its surface. The electronics may alsoinclude more complex electronic circuits associated with the particularapplications. Application specific circuits, e.g., microprocessors andmemory for a laptop computer can be fabricated as well, furtherincreasing the degree of integration.

[0103]FIGS. 17A and 17B show two drive/connection schemes. Direct driveis illustrated by a seven segment display 1700. A common conductor 1702connects all of the segments 1703 in parallel. In addition, separatesegment conductors 1704 go to each segment individually. As shown inFIG. 17B, in a detailed corner 1712 of one segment, an array of IMods1708 are connected in parallel and would be connected as a group to asegment conductor 1704 and the common conductor 1702. The generalmicroscopic nature of this type of IMod structure makes it necessary togroup the IMods together to form larger elements to allow for directviewing of the display. Application of a voltage between a selected oneof the segment conductors and the common conductor actuates all of theIMods within that segment. The direct drive approach is limited by thefact that the number of conductors becomes prohibitive if the number ofgraphical elements gets large enough.

[0104] Referring to FIGS. 18A and 18B, an active matrix drive approachis shown. Row lines 1800 and column lines 1804 result in atwo-dimensional array the intersections of which provide pixel locationssuch as 1802. As seen in FIG. 18B, each of the pixel locations 1802 maybe filled with an array of parallel connected IMods 1803. In this schemea common conductor 1808 may be connected to the row line, and the IModarray conductor, 1810, may be connected to the column line, though thiscould be reversed.

Product and Device Applications

[0105] The remaining figures illustrate product and device applicationswhich use the fabrication, drive, and assembly techniques described thusfar.

[0106] The IMod as an easily fabricated, inexpensive, and capablemodulator can be placed in an exceptional number of roles which requirethe manipulation of light. These areas fall into at least twocategories: IMods which are used to modulate or otherwise affect lightfor purposes which do not result in direct visually perceivedinformation (embedded applications); and IMods which are used to conveycodified, abstract or other forms of information via light to bevisually perceived by an individual (perceived applications). All ofthese applications, both embedded and perceived, can be roughly dividedaccording to array size and geometry, however these boundaries are fordescriptive purposes only and functional overlap can exist across thesecategories. They do not represent an exhaustive list of possibilities.

[0107] One category of applications utilizes single or individualmodulators which are generally for embedded applications. These may becoupled to optical fibers or active electronics to provide, among otherthings, a mechanism for selecting specific frequencies on a wavelengthdivision multiplexed fiber-optic communication system, as well as a lowdata rate passive fiber optic modulator. Single modulators may becoupled to semiconductor lasers to provide, among other things, amechanism for selecting specific frequencies transmitted by the laser,as well as a low data rate laser modulator. Single modulators may becoupled to optical fibers, lasers, or active electronics to alter thephase of light reflected.

[0108] Linear arrays, though generally for embedded applications, alsobegin to have potential in perceived roles. Devices for printing imagerymay utilize a linear array as the mechanism for impressing informationon to reflected or transmitted light which is subsequently recorded in alight sensitive medium. Devices for scanning images may utilize a lineararray to select different colors of a printed or real image forsubsequent detection by a light sensitive device.

[0109] Yet another category of applications includes microscopictwo-dimensional arrays of IMods which may be used to providereconfigurable optical interconnects or switches between components.Such arrays may also be used to provide optical beam steering ofincident light. Using a lens system, to be discussed later, may allowsuch an array to be readable.

[0110] Small arrays, on the order of 2″ square or smaller, may find avariety of uses for which this size is appropriate. Applications includedirect view and projection displays. Projection displays can be usedindividually or in arrays to create virtual environments (VEs). Atheater is an example of a single channel VE, while an omnimax theater,with many screens, represents a multi-channel virtual environment.Direct view displays can be used for alphanumeric and graphic displaysfor all kinds of consumer/commercial electronic products such ascalculators, cellular phones, watches and sunglasses (active or static),jewelry, decorative/informative product labels or small format printing(business card logos, greeting card inserts, product labels logos,etc.); decorative clothing patches or inserts (sneakers, badges, beltbuckles, etc.); decorative detailing or active/static graphic printingon products (tennis rackets, roller blades, bike helmets, etc.); anddecorative detailing or active/static graphic printing on ceramic,glass, or metal items (plates, sculpture, forks and knives, etc.). Verylarge (billboard sized) displays may be produced by combining arrays ofsmall arrays which are themselves directly driven. Embedded applicationsmay include spatial light modulators for optical computing and opticalstorage. Modulator arrays fabricated on two dimensional light sensitivearrays, such as CCDs, may be used as frequency selective filter arraysfor the selection of color separations during image acquisition.

[0111] Another size category of devices, medium arrays, may be definedby arrays of roughly 2″ to 6″ square. These include direct view displaysfor consumer electronic products including organizers, personal digitalassistants, and other medium sized display-centric devices; controlpanels for electronic products, pocket TVs, clock faces (active andstatic); products such as credit cards, greeting cards, wine and otherproduct labels; small product exteriors (walkmen, CD cases, otherconsumer electronic products, etc.); and larger active/static graphicalpatches or inserts (furniture, clothing, skis, etc.)

[0112] For arrays on the order of 6″ to 12″ square, large arrays, thereexist other compelling applications. These include direct view displaysfor large format display-centric products (TVs, electronic readers fordigital books, magazines and other traditionally printed media, specialfunction tools); signs (window signs, highway signs, public informationand advertising signs, etc.); large consumer product exteriors/activesurfaces and body panels (microwave oven, telephone, bicycle, etc.) ;and furniture exteriors and lighting fixtures, high end products. Directview 3-D displays and adaptive optics are also possible.

[0113] Arrays approximately 12″ square or larger, and aggregate arrays(which are combinations of smaller arrays to achieve a larger one) ,further define a unique set of devices, and provide the potential toaffect our overall environment. These include direct view displays forvery large formats (billboards, public spaces, highway,industrial/military situation displays, etc.); Body panels and activeexteriors for very large products (cars, motorcycles, air and watercraft, sails, refrigerators); and active/static exteriors/interiors forvery large objects (buildings, walls, windows).

[0114] In FIG. 19, a fiber optic detector/modulator 1901 includes asingle IMod 1904. An optical fiber 1900 is bonded to substrate 1902.IMod 1904 resides on the substrate which is bonded to backplate 1910 bya seal 1908 using anodic bonding for example. The backplate also servesas a substrate for detector 1906. Electronics 1912 are mounted onsubstrate 1902 via chip-on-glass or some other previously describedtechnique. Device 1901 could provide a number of functions depending onthe nature of the IMod. For example, a reflective mode IMod could act asa modulator of light which is incident through the optical fiber. Usinga design which switches between absorbing or reflecting, the intensityof the reflected light may be modulated. Using a transmissive IMod, thedevice could act as a transceiver. Switching the IMod between fullytransmissive or fully reflective would also modulate the reflected lightand thus perform as a data transmitter. Holding it in the fullytransmissive state would allow the detector 1906 to respond to lightincident through the fiber, thus acting like a receiver. Use of atunable IMod would allow the device to act as a frequency sensitivedetector, while not precluding modulation as well.

[0115] Referring to FIGS. 20 and 21A, a linear array 2104 of IMods 2001,2003, 2005 is supported on a substrate 2004. Each of the IMods includesa primary mirror 2006, a secondary mirror 2002, electrodes 2008, supportarms 2000, and support plate 2010. Each IMod would be driven separatelyin a binary or analog fashion depending on the application. In therepresentative application shown in FIG. 21A, a transport mechanism 2106moves a medium 2108 past a linear IMod array 2104 (the axis of the arrayis into the page). Two potential applications for such a configurationcould include image acquisition or digital printing. In acquisitionmode, component 2100 is a detector array which is coupled to IMod array2104 via lens system 2102. Component 2110 acts as a light source,illuminating pre-printed images which reside on media 2108. By using theIMod as a tunable filter array, specific colors of the image on themedia may be selected and detected, allowing for high resolution captureof graphical information residing on the media.

[0116] Alternatively, component 2100 could be a light source which useslens system 2102 to couple and collimate light through IMod array 2104onto media 2108. In this case, the media would be a photosensitivematerial which would undergo exposure as it passed beneath the array.This would provide a mechanism for the printing of high resolution colorimages. No electronic components reside on the array substrate in thisexample. FIG. 21B shows a components diagram illustrating one way inwhich this product could be implemented using off-the-shelf components.In this case, they comprise a central controller 2112, (includingprocessor 2114, memory 2116, and low level I/O 2118), high level I/Ocomponents (user interface 2120 and logic 2122, detector array 2130),control components (light source 2132, media transport 2128 and logic2126), display 2140 (logic 2138, drivers 2136, IMod array 2134) andpower supply 2124. The central controller handles general purposeoperational functions, the high level I/O components and display dictatehow information gets in and out of the product, and the controllercomponents manipulate peripheral devices.

[0117] Referring to FIG. 22, a two-dimensional IMod device 2201 isfabricated directly on a photosensitive detector array 2206 such as acharge coupled device (CCD) or other light sensitive array. Array 2206has photosensitive areas 2202 and charge transport and IMod driveelectronics 2204. Planarization layer 2208, deposited on the CCD,provides a flat surface for the fabrication of the IMod array 2200. Sucha layer could be in the form of a curable polymer or spun-on oxide.Alternatively, some form of chemical mechanical polishing might be usedto prepare an optically smooth surface on the integrated circuit. Device2201 provides a fully integrated 2-D, tunable light detection systemwhich can be used for image capture or image printing (if the detectoris replaced with a light source).

[0118]FIG. 23 illustrates a digital camera 2301 based on this device.Camera body 2300 provides mechanical support and housing for lens system2304 and electronics and IMod detector array 2302. Scene 2306 is imagedon the surface of the array using the lens system. By tuning the IModarray to the frequencies of light corresponding to red, green, and blue,a full color image may be acquired by combining successive digitalexposures. Hyperspectral imagery (in other wavelength regions such asultraviolet or infrared) may be obtained by tuning to frequenciesbetween these points. Because of the high switching speed of the IMods,all three images may be acquired in the time it takes a conventionalcamera to capture one.

[0119] Referring to FIG. 24A, an application for smallsized displays isa digital watch 2400 (the back side of the watch is shown in FIG. 24A)which includes a reflective IMod display at its core. The IMod displaycomprises an IMod array 2402 and drive electronics, 2404. The display(see examples in FIGS. 24B-24E) could vary in complexity from separategraphic elements driven in a direct drive manner, to a dense array usingactive matrix addressing, or some combination. The electronics could befabricated on glass using polysilicon or amorphous silicon transistors,or MEM switches. While the direct drive approach would still exploit thesaturated appearance of the IMod, a dense array would allow for theselection of arbitrary or pre-programmed graphical patterns such as FIG.24B. This would add an exciting new fashion component to watches notunlike the art oriented Swatch® only in electronic form. Owners couldselect from a series of preprogrammed displays 2408 (FIG. 24D), say bypushing the stem, or download limited edition displays digitally fromtheir favorite artists.

[0120] Referring to FIG. 25A, a small transmissive IMod array is shownin a head mounted display 2511. Support 2508 provides a frame formounting the display components and the viewer screen 2512. Referringalso to FIG. 25B, the display includes a light source 2500, an IModarray 2502, a lens system 2504, and a reflector 2506. The display isused in indirect mode with the image formed on screens 2512 for thebenefit of viewer 2510. Alternatively, the IMod array could be formeddirectly on the screen itself and thus be used in direct view mode. Inboth cases, the display could function to provide aesthetic imagerywhich could be seen by other individuals and provide an appealingdynamic external look.

[0121] Referring to FIGS. 26A through 26D, an IMod display 2604 is shownin a product with a very wide range of applications. In this case, thedisplay is used in direct view mode, and could come in a variety ofsizes depending on the specific product, but ranging in size fromseveral inches across to about one foot diagonal. The primary goal isfor a device that has a very small footprint and/or is portable, and thescheme is to facilitate mobility. The device 2600 could be described asa personal information tool, a portable digital assistant, a webbrowser, or by various other titles which are only now being coined todescribe this class of products. In general its purpose would be toserve as a media interface for a variety of information gathering,processing, and dissemination functions, or as a mobile or stationaryperipheral for a centralized processing station to which it isconnected, perhaps via the internet or some wireless communicationsmedium. A specialized peripheral in a home-based application might be akitchen cooking assistant which would be portable and present easilyreadable recipes by virtue of the display and the fact that most of itsprocessing is located in some other unit. Many other variations on thistheme are possible. This tool comprises a display 2604 and some basiccontrols 2602. Internal components would include some combination ofprocessing electronics, information storage, and communicationshardware. Representative products range from personal organizers anddigital books and magazines, to application specific tools(construction, medical, scientific) or tools for browsing the internet.Techniques for operating such a tool are varied and could range fromvoice recognition, to touch sensitive screens. However, all of theproducts would have the ability to digitally display graphicalinformation using reflected (preferred) or transmitted light with highlysaturated colors. Because it is digital, the complexity and cost of thedriving electronics would be significantly reduced, and because it canuse reflected light, the power consumption is extremely low while theperformance remains high. These two characteristics make such a highperformance display oriented product viable from an economic andportability perspective. FIG. 26C is an example of one kind of personalcommunications device, a cellular phone in this case though the pager ofFIG. 26D is an example of another. Display 2608 is capable of displayingboth graphical and text information. FIG. 26B shows a components diagramillustrating one way in which these products could be implemented usingavailable off-the-shelf components. In this case, they comprise acentral controller 2610 (including processor 2612, memory 2614, and lowlevel I/O 2616), high level I/O components (user interface 2618 andlogic 2620, audio I/O 2624, digital camera 2628, and wireless tranceiver2630) , display 2638 (logic 2636, drivers 2634, IMod array 2632) andpower supply 2622. The central controller handles general purposeoperational functions, while high level I/O components dictate howinformation gets in and out of the product.

[0122] Referring to FIG. 27A through 27G, several applications are shownwhich emphasize the aesthetic nature of an IMod display as well as itsinformation conveying aspect. An IMod display could be included in aportable compact disc player 2700 of the kind that serves as a commoditystatus device made by many manufacturers. By virtue of an IMod display,a larger fraction of the exterior of the player may be devoted toinformation display functions, indicating status of the device as wellas tracks playing. Because it consumes such a large fraction of theexterior, it would be possible to have the display play a moresignificant role in the appearance of the CD player. Static as well asdynamic patterns and images could be displayed which may or may not haveany connection with the status of the player. However, because of therich saturated colors, the appearance becomes a significant and distinctselling point for the manufacturer. This concept holds true for anynumber of consumer electronic devices whose form and function could beenhanced by an active exterior. A microwave oven which pulsed red whenthe food was done, or a bread baking machine whose exterior changedcolors as the baking process progressed are just two examples. FIG. 27Cshows a components diagram illustrating one way the CD player could beimplemented using off-the-shelf components. In general, they comprise acentral controller 2706 (including processor 2707, memory 2710, and lowlevel I/O 2712), high level I/O components (user interface 2702 andlogic 2704) , display 2722 (logic 2720, drivers 2718, IMod array 2716)disc player mechanism 2714, and power supply 2724. The centralcontroller handles general purpose operational functions, high level I/Ocomponents dictate how information gets in and out of the product, andthe disc play mechanism manipulates mechanical servos.

[0123] The skis of FIG. 27D and the sneaker of FIG. 27F are examples ofconsumer goods which could benefit purely from the aesthetic potentialfor an active exterior. In both cases, an IMod array has been fabricatedon a substrate, for example flexible plastic, along with electronics andintegrated into the product using any number of techniques currentlyused for incorporating or laminating composite pieces into fabric orsolid composites. Power could be supplied by piezoelectric like deviceswhich convert the mechanical power of movement (e.g., ski flexing orwalking) into electricity. Remote control, FIG. 27E, could be used toeffect control over the images displayed. Further control could beexhibited to reflect the mode of use of the product. In the case of theskis, the pattern might become more dynamic as the skier gained speed,or in the case of the shoes the strength of the runner's stride. Theseare only a few of the possibilities for the aesthetic enhancement ofconsumer goods by the use of a dynamic exteriors. FIG. 27G illustrateshow a display could respond to the state of the consumer product. Thecontrol mechanism would consist of a sensor 2730, which could detectvibration (in a shoe or ski) or temperature (in a turkey), program logic2732, which would interpret the sensor output and provide preprogrammed(or reprogrammable) images or image data to display 2734, communicationsinput/output 2738, and display control electronics 2736.

[0124] Referring to FIGS. 28A and 28B, even larger IMod arrays are shownincorporated into the exterior of an automobile. In this case bodypanels 2800, 2802 as well as windows 2804, could use reflective andtransmissive IMod designs respectively. Dynamic control of the exteriorappearance of a car would be a very appealing option for the owner,providing the ability for the owner to customize the appearance himself,or to “download” exteriors in a digital fashion. Such a control 2806could take the form of a small panel integrated into the dashboard whichdisplayed various exteriors under button control. The same techniquescould be applied to other highly style oriented goods in the class andfunctional category, including motorcycles, sailboats, airplanes andmore. FIG. 28B shows a components diagram illustrating one way in whichthis product could be implemented using off-the-shelf components. Ingeneral, they comprise a central controller 2808 (including processor2810, memory 2812, and low level I/O 2814), high level I/O components(user interface 2816, and logic 2818), display 2828 (logic 2826, drivers2824, IMod array 2822) and power supply 2820. The central controllerhandles general purpose operational functions, while high level I/Ocomponents dictate how information gets in and out of the product.

[0125] Referring to FIGS. 29A through 29D, billboard-sized arrays 2900of IMod display segments could be assembled and replace current staticdisplays used for advertising and public service announcements. Display2900 would include reflective devices to be illuminated by ambient lightor a supplemental light source 2902. A large display could be assembledfrom individual segments 2904 (FIG. 29B) which would support segmentpixels 2906. Each segment pixel would include three sets of sub-pixelarrays 2910, 2912, and 2914, which would reside on pixel substrate 2908(FIG. 29C). The resulting large displays could range from placards onthe sides of buses and inside of subways, to billboards, to entirearchitectural structures such as homes or skyscrapers. In FIG. 30A,skyscraper 3000 is an example of a large building which exploits theaesthetic and cheap manufacture of the IMod array. All of the glass usedin the manufacture of such structures is coated with thin films up to 4or more layers thick to provide energy efficient coatings. Similiarcoating techinques could be applied to the manufacture of the IModarrays. FIG. 30B shows a components diagram illustrating one way inwhich both of these products could be implemented using off-the-shelfcomponents. In this case, they comprise a central controller 3002(including processor 3004, memory 3006, and low level I/O 3006), highlevel I/O components (PC based user interface 3008), display 3020 (logic3018, drivers 3016, IMod array 3014), lighting control 3012, and powersupply 3010. The central controller handles general purpose operationalfunctions, high level I/O components dictate how information gets in andout of the product, and the controller components manipulatesupplementary lighting and peripheral components.

[0126] It should be noted that several alternative display technologiesmay also be applicable to some of the less rigorous aestheticapplications, in particular, small AMLCDs, LCDs fabricated on activecrystalline silicon, field emission displays (FEDs), and possibly plasmabased displays. These technologies are deficient due to their price,manufacturing complexity, and non-reflective (emissive) operation.However, certain high-end fashion oriented products (luxury watches,jewelry and clothing) may command a price and provide an environmentwhich could make these viable approaches. Organic emitters could beparticularly suited for exterior applications which are not necessarilyexposed to environmental extremes and which might be seen in dimly litsituations. They are the only emissive technology which offers thepotential for very lowcost and ease of manufacture. The Alq/diaminestructures and poly(phenylene vinylene) materials, which were describedbefore, could be patterned and directly addressed on a variety ofsubstrates (plastic clothing inserts for example) to provide dynamicexteriors.

[0127]FIG. 31A shows interferometric particles suspended in a liquidcrystal medium, 3100, making possible full color liquid crystal displaysbased on the controlled orientation of the particles within the medium.As shown in FIG. 31B, application of a voltage between electrodes 3102from source 3104 causes the particles to be driven from their randomquiescent orientation 3106 defined by the liquid crystal and thesurfaces of the substrate into an orderly orientation 3108. When theparticles are randomly oriented, light of a specific color 3110 isreflected. When the particles are ordered, light 3112 passes through.

[0128] Referring to FIG. 32A, two kinds of projection display units,3200 and 3202, are shown. Each unit comprises components consisting oflight source/optics 3206, electronics 3204, projection optics 3210, andIMod array 3208. While the IMod array in projector 3200 is designed foruse in transmission mode, the IMod array in projector 3202 is designedfor use in reflection mode. The other components are essentially thesame with the exception of the need to modify the optics to accommodatethe difference in the nature of the optical path. Screen 3212 shows arepresentative projected image. FIG. 32B shows a components diagramillustrating one way in which this product could be implemented usingoff-the-shelf components. In this case, they comprise a centralcontroller 3212 (including processor 3214, memory 3216, and low levelI/O 3218), high level I/O components (user interface 3220 and logic3222), display 3236 (logic 3234, drivers 3232, IMod array 3230)focus/light source control 3226, and power supply 3224. The centralcontroller handles general purpose operational functions, high level I/Ocomponents dictate how information gets in and out of the product, andthe controller components manipulate peripheral devices.

[0129] An application in chemical analysis is illustrated in FIG. 33A.Transparent cavity 3300 is fabricated such that gas or liquid medium3302 may pass through its length. Light source 3304 is positioned toproject broad spectrum light through the medium into tunable IMod array3306. This array could be coupled to a fiber 3308, or reside on adetector array with 3308 acting as data link to electronics 3310. Byspectrally analyzing the light which passes through the medium, much canbe determined about its composition in a compact space. Such a devicecould be used to measure the pollutants in an air stream, the componentsin a liquid, separations in an chromatographic medium, fluorescingcompounds in a medium, or other analytes which can be measured usinglight, depending on the frequency of the light source. FIG. 33B shows acomponents diagram illustrating one way in which this product could beimplemented using off-the-shelf components. In this case, they comprisea central controller 3312 (including processor 3314, memory 3316, andlow level I/O 3318), high level I/O components (user interface 3320, andlogic 3322), IMod drivers 3330 and IMod 3328, light source 3326 , andpower supply 3324. The central controller handles general purposeoperational functions, high level I/O components dictate how informationgets in and out of the product, and the controller components manipulateperipheral devices.

[0130]FIG. 34A illustrates an automotive application from a driver'sviewpoint. FIG. 34B represents a side view of the windshield anddashboard. A direct view graphical display 3404 portrays a variety ofinformation, for example, an enhanced view of the roadway. An imagegenerated in the windshield via a heads-up display. Such a display is avariation on the previously discussed projection system. In this case,the inside of the windshield acts as a translucent projection screen,and the projector 3406 is mounted in the dashboard. Automotiveapplications have very stringent requirements for heat, and UVstability, as well as high brightness ambient conditions which would beideal for an IMod application. FIG. 34C shows a components diagramillustrating one way in which these products could be implemented usingoff-the-shelf components. In this case, they comprise a centralcontroller 3410 (including processor 3412, memory 3414, and low levelI/O 3416), high level I/O components (user interface 3418, digitalcamera 3428, auto sensors 3424), display 3436 (logic 3434, drivers 3432,IMod array 3430) and power supply 3422. The central controller handlesgeneral purpose operational functions, high level I/O components dictatehow information gets in and out of the product, and the controllercomponents manipulate peripheral devices.

[0131]FIG. 35A portrays an application involving an instrument panel, inthis case an oscilloscope 3500, though many kinds of special purposetools could benefit from a graphical display. In this situation, display3502, is used to show a waveform plot but could also, as describedpreviously, display text, or combinations of graphics and text. Portablelow-power tools for field use would benefit greatly from a full-colorfast response FPD. FIG. 35B shows a components diagram illustrating oneway in which these products could be implemented. All of the componentsare available off-the-shelf and could be configured by one who isskilled in the art. In this case, they comprise a central controller3508 (including processor 3510, memory 3514, and low level I/O 3516),high level I/O components (user interface 3518 and logic 3520), display3534 (logic 3532, drivers 3530, IMod array 3528) and power supply 3522.The central controller handles general purpose operational functions,while high level I/O components dictate how information gets in and outof the product.

[0132] Other embodiments are within the scope of the following claims.

What is claimed is:
 1. A modulator of light comprising an interferencecavity for causing interference modulation of the light, the cavityhaving a mirror, the mirror comprising a corrugated surface.
 2. Amodulator of light comprising an interference cavity for causinginterference modulation of the light to produce a color conditionvisible to an observer, the color condition being determined by thespatial configuration of the modulator.
 3. The modulator of claim 2wherein the interference cavity comprises a mirror and a supportingstructure holding the mirror, and wherein the spatial configurationcomprises the configuration of the supporting structure.
 4. Themodulator of claim 2 wherein the interference cavity comprises p1 amirror, and wherein the spatial configuration comprises patterning ofthe mirror.
 5. The modulator of claim 2 wherein the interference cavitycomprises a mirror, and a supporting structure holding the mirror, andwherein the supporting structure is coupled to a rear surface of themirror.
 6. A structure for modulating light comprising modulators oflight each including an interference cavity for causing interferencemodulation of the light, each of the modulators having a viewing cone,the viewing cones of different ones of the modulators being aligned indifferent directions.
 7. The structure of claim 6 in which the viewingcones of the different modulators are aligned in random directions. 8.The structure of claim 6 in which the viewing cones of the modulatorsare narrower than the viewing cone of the overall structure.
 9. Astructure for modulating light comprising modulators of light eachincluding an interference cavity for causing interference modulation ofthe light, and a liquid medium in which the modulators are suspended.10. A structure for modulating light comprising modulators of light eachincluding an interference cavity for causing interference modulation ofthe light, and an optical compensation mechanism coupled to themodulators which enhances the optical performance of the structure. 11.The structure of claim 10 in which the mechanism comprises a combinationof one or more of a holographically patterned material, a photoniccrystal array, a multilayer array of dielectric mirrors, or an array ofmicrolenses.
 12. The structure of claim 1 wherein the brightness and/orcolor are controlled by error diffusion.
 13. A modulator of lightcomprising an interferometric modulator, and an optical fiber coupled tothe interferometric modulator.
 14. The application of claim 13 whereinthe IMod is used in the analysis of chemical, organic, or biologicalcomponents.
 15. An information printing system comprising an array ofinterference modulators of light, a lens system, and a media transportmechanism.
 16. An image capture system comprising an array ofinterference modulators of light, a lens system, and a media transportmechanism.
 17. An information projection system comprising an array ofinterference modulators of light, a lens system, mechanical scanners,and control electronics.
 18. The system of claim 17 in which the controlelectronics are configured to generate projected images for virtualenvironments.
 19. The application of claim 18 in which the arrayincludes liquid crystals or microelectromechanical modulators.
 20. Aproduct comprising an operational element, a display element, a housingenclosing the operational element and having a display element, thedisplay element including a surface viewed by a user, and an array ofinterference modulators of light on the surface.
 21. The product ofclaim 20 in which the operational element comprises a personalcommunications device.
 22. The product of claim 20 in which theoperational element comprises a personal information tool.
 23. Theproduct of claim 20 in which the operational element comprises avehicular control panel.
 24. The product of claim 20 in which theoperational element comprises an instrument control panel.
 25. Theproduct of claim 20 in which the operational element comprises a timekeeping device.
 26. The product of claim 20 in which the operationalelement comprises an article of clothing or portion thereof.
 27. Theproduct of claim 20 in which the operational element comprises an itemof jewelry.
 28. The product of claim 20 in which the operational elementcomprises a sporting good.
 29. The product of claim 20 in which thearray substantially alters the aesthetic or decorative features of thesurface.
 30. The product of claim 29 in which the aesthetic componentresponds to a state of use of the consumer product.
 31. The product ofclaim 29 in which the aesthetic component is downloaded or derived froman external source.
 32. The product of claim 29 wherein the array alsoprovides information.
 33. The application of claim 29 wherein liquidcrystals, field emission, plasma, or organic emitter based technologiesand associated electronics are used as the modulation array.
 34. Thedevice of claim 1 comprising an application incorporating aggregatearrays of IMods.
 35. The application of claim 34 wherein the array isused to display information on signs or billboards.
 36. A vehiclecomprising a body panel, an array of interference modulators of light ona surface of the body panel, and electronic circuitry for determiningthe aesthetic appearance of the body panel by controlling the array ofinterference modulators.
 37. A building comprising external surfaceelements, an array of interference modulators of light on a surface ofthe body panel, and electronic circuitry for determining the aestheticappearance of the surface elements by controlling the array ofinterference modulators.
 38. A full color active display comprising aliquid crystal medium, and interferometric elements embedded in themedium.
 39. A structure comprising a substrate, micromechanical elementsformed on the surface of the substrate, and electronics connected tocontrol the elements, the electronics being formed also on the surfaceof the substrate.